Lane keeping assist system and method for improving safety in preceding vehicle follower longitudinal control

ABSTRACT

A lane keeping assist system and method for increasing safety in preceding vehicle follower longitudinal control are disclosed. The lane keeping assist system for performing lane keeping using information about a lane and peripheral vehicle includes an image sensor configured to detect a forward lane and a preceding vehicle with respect to a host vehicle, and an electronic control unit (ECU) configured to control a traveling direction of the host vehicle in a manner that the host vehicle follows a traveling route within the detected lane, perform a preceding vehicle follower control to control the traveling direction of the host vehicle in a manner that the host vehicle follows the preceding vehicle if the lane is not detected, and restrict a follower longitudinal control if the preceding vehicle deviates from an expected path of travel. Thus, the ECU controls a vehicle to safely enter an entrance of a highway service station nearest to a current highway in which the vehicle is traveling, resulting in greater driver convenience.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation Application of U.S. patentapplication Ser. No. 16/218,163, filed Dec. 12, 2018, which is based onand claims priority under 35 U.S.C. § 119 to Korean Patent ApplicationNo. 10-2018-0049216, filed on Apr. 27, 2018, the disclosures of each ofwhich are incorporated herein by reference in their entireties.

BACKGROUND 1. Field

Embodiments of the present disclosure relate to a lane keeping assistsystem (LKAS) and a method for controlling the same, and moreparticularly to a lane keeping assist system (LKAS) for restricting apreceding vehicle follower longitudinal control range in a precedingvehicle follower longitudinal control process caused by disappearance orloss of a forward lane when lane keeping control is performed throughrecognition of a lane and a preceding vehicle, resulting in improvementin vehicle safety, and a method for controlling the same.

2. Description of the Related Art

Generally, an Advanced Driver Assistance System (ADAS) may autonomouslyrecognize some of many situations capable of occurring during vehicledriving, and may determine what situations have occurred, such that theADAS can autonomously control mechanical devices based on the determinedsituations. The Advanced Driver Assistance System (ADAS) may beimplemented by integrating an Adaptive Cruise Control (ACC) system, aLane Keeping Assist System (LKAS), and navigation information (map data,GPS data, etc.), such that the ADAS can greatly mitigate driverdifficulty during vehicle driving. In this case, the ACC system maydetermine a preceding vehicle to be a control object using vehicledetection information sensed by one or more sensors, and mayautonomously control a driving speed and a distance between a hostvehicle and a peripheral vehicle through acceleration/decelerationcontrol. The LKAS may perform lane keeping by adjusting a travelingdirection of a host vehicle.

The Lane Keeping Assist System (LKAS) may detect a lane and a precedingvehicle using a front-view camera, may plan a traveling route within alane, and may control a host vehicle to follow a target route usingactive control of an electronic power steering device, thereby providinga driver of the host vehicle with high convenience. If unexpected lanedeparture is detected, the LKAS may adjust a traveling direction of thehost vehicle using active control of the electronic power steeringdevice, such that the LKAS can assist the driver in easily driving thevehicle.

However, during lateral control based on lane recognition that isachieved through a camera as shown in FIG. 6A, when a lane capable ofbeing temporarily recognized in road situations such as a crossroad orcrosswalk is not present or deterioration of lane recognitionperformance occurs, the conventional LKAS may activate a function ofallowing a host vehicle to follow a preceding vehicle due to thepresence of a lane. In this case, when a preceding vehicle deviates froman estimated route by performing lane change during preceding vehiclefollower longitudinal control as shown in FIG. 6B, an unexpected erroroccurs in lane keeping control, such that the conventional LKAS may havea high possibility of collision with a peripheral vehicle present inlateral directions with respect to the host vehicle.

CITED REFERENCES Patent Documents

-   Korean Patent Laid-Open Publication No. 2017-0119877 (2017.10.30)-   Korean Patent Laid-Open Publication No. 2017-0014163 (2017.02.08)

SUMMARY

Therefore, it is an aspect of the present disclosure to provide a lanekeeping assist system (LKAS) for restricting a preceding vehiclefollower longitudinal control range in a preceding vehicle followerlongitudinal control process caused by disappearance or loss of aforward lane when lane keeping control is performed through recognitionof a lane and a preceding vehicle, resulting in improvement in vehiclesafety, and a method for controlling the same.

Additional aspects of the invention will be set forth in part in thedescription which follows and, in part, will be recognized by those ofskill in the art upon understanding of the description, or may belearned by practice of the invention.

In accordance with an aspect of the present disclosure, a lane keepingassist system for performing lane keeping using information about a laneand peripheral vehicle includes a lane and preceding vehicle sensorconfigured to detect a forward lane and a preceding vehicle with respectto a host vehicle, a vehicle dynamics sensor configured to detect adriving speed, a steering angle, and a yaw rate of the host vehicle, andan electronic control unit (ECU) configured to control a travelingdirection of the host vehicle in a manner that the host vehicle followsa traveling route within the detected lane, control the travelingdirection of the host vehicle in a manner that the host vehicle followsthe preceding vehicle when the lane is not detected, and restrict afollower longitudinal control range according to movement of thepreceding vehicle.

The electronic control unit (ECU) includes a lane and preceding vehiclerecognition module configured to recognize lane information andpreceding vehicle information by acquiring lane and preceding vehicledetection information from the lane and preceding vehicle sensor, aroute generation module configured to generate a route in a manner thatthe host vehicle travels in a center part based on the recognized laneinformation, generate a new route based on the recognized precedingvehicle information when the lane information is not recognized, andrestrict a follower longitudinal control range according to movement ofthe preceding vehicle, and a target steering torque calculation moduleconfigured to calculate a target steering torque needed for the hostvehicle following the route generated by the route generation module,and transmit the calculated target steering torque to an electronicpower steering device.

The route generation module may restrict the follower longitudinalcontrol range when the preceding vehicle deviates from the new route.

The lane information may include at least one of a horizontal positionof the host vehicle located in the lane, a direction angle between thehost vehicle and the lane, a curvature of the lane, and a curvaturechange rate of the lane. The preceding vehicle information may includeat least one of a horizontal/vertical distance between the host vehicleand the preceding vehicle, a difference in proceeding direction angle,etc.

If the lane is not recognized, the route generation module may generatea virtual lane formed by extension of a legacy lane in consideration ofa curvature based on finally-recognized lane information, and maygenerate a virtual route in a manner that the host vehicle travels in acenter part of the generated virtual lane.

The route generation module may calculate a position and direction angleof the host vehicle present on the virtual route using a vehicledynamics sensor, may calculate a horizontal position about the virtualroute of the preceding vehicle by reflecting the preceding vehicleinformation in the calculated information, and may restrict the followerlongitudinal control range when the calculated horizontal position aboutthe virtual route of the preceding vehicle deviates from the virtualroute by a predetermined horizontal distance or greater.

In accordance with another aspect of the present disclosure, a lanekeeping assist method includes, if a lane keeping assist systemconfigured to perform lane keeping using information about a lane andperipheral vehicle is turned on, detecting a forward lane of a hostvehicle, controlling a traveling route of the host vehicle in a mannerthat the host vehicle follows a traveling route within the detected lanewhen the lane is detected, or generating a virtual lane when the lane isnot detected in a manner that the host vehicle travels in a center partof the virtual lane, detecting a preceding vehicle located in a forwardregion of the host vehicle, and stopping deactivate of the lane keepingassist system when the preceding vehicle is not detected, or controllinga traveling direction of the host vehicle when the preceding vehicle isdetected in a manner that the host vehicle follows the preceding vehicleaccording to movement of the preceding vehicle.

The virtual lane may be formed by extension of a legacy lane on thebasis of finally-recognized lane information.

The lane information may include at least one of a horizontal positionof the host vehicle located in the lane, a direction angle between thehost vehicle and the lane, a curvature of the lane, and a curvaturechange rate of the lane. The preceding vehicle information may includeat least one of a horizontal/vertical distance between the host vehicleand the preceding vehicle, a difference in proceeding direction angle,etc.

The controlling the traveling route of the host vehicle so as to allowthe host vehicle to follow the preceding vehicle may include stoppingdeactivate of the lane keeping assist system when the preceding vehicledeviates from the virtual route.

The controlling the traveling direction of the host vehicle so as toallow the host vehicle to follow the preceding vehicle may includecalculating a horizontal position of the preceding vehicle within thevirtual route, determining whether the preceding vehicle travels in apreceding vehicle follower longitudinal control range of the virtualroute on the basis of the horizontal position of the preceding vehiclein the virtual route, and controlling the traveling direction of thehost vehicle when the preceding vehicle travels in the preceding vehiclefollower longitudinal control range such that the host vehicle followsthe preceding vehicle during traveling of the preceding vehicle, anddeactivating the lane keeping assist system when the preceding vehicledeviates from the virtual route by a predetermined horizontal distanceor greater.

A reference value of the follower longitudinal control range may be setto a width of a final lane centering around the virtual route.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects of the invention will become apparent andmore readily appreciated from the following description of theembodiments, taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 is a block diagram illustrating a lane keeping assist system(LKAS) according to an embodiment of the present disclosure.

FIG. 2A is a conceptual diagram illustrating lane information recognizedby a lane and preceding vehicle recognition module, and FIG. 2B is aconceptual diagram illustrating preceding vehicle information recognizedby a lane and preceding vehicle recognition module.

FIG. 3 is a conceptual diagram illustrating a method for deactivatingpreceding vehicle follower longitudinal control when a preceding vehicledeviates from a preceding vehicle follower longitudinal control rangeafter a route generation module determines whether lane departure of thepreceding vehicle has occurred using final lane information according toan embodiment of the present disclosure.

FIG. 4 is a conceptual diagram illustrating a method for allowing aroute generation module to generate a virtual lane based on final lanerecognition information in a lane disappearance section in which a laneis lost or washed away according to an embodiment of the presentdisclosure.

FIG. 5 is a flowchart illustrating an overall process of a lane keepingassist (LKA) method according to an embodiment of the presentdisclosure.

FIG. 6A is a conceptual diagram illustrating a method for allowing aconventional lane keeping assist system (LKAS) to perform lateralcontrol based on lane recognition according to the related art.

FIG. 6B is a conceptual diagram illustrating a method for allowing aconventional lane keeping assist system (LKAS) to perform vehiclefollower longitudinal control in a lane disappearance state duringlateral control based on lane recognition.

DETAILED DESCRIPTION

Advantages and features of the present disclosure and a method ofachieving the advantages and features of the present disclosure will beclearly understood from embodiments described hereinafter in conjunctionwith the accompanying drawings. However, the present disclosure is notlimited to the following embodiments and may be realized in variousdifferent forms. These embodiments are provided only to completelydisclose the present disclosure and for a person having ordinary skillin the art to which the present disclosure pertains to completelyunderstand the category of the disclosure. That is, the presentdisclosure is defined only by the claims. The same reference numberswill be used throughout this specification to refer to the same parts.

A lane keeping assist system (LKAS) and a method for controlling thesame according to an embodiment of the present disclosure willhereinafter be described with reference to the attached drawings.

FIG. 1 is a block diagram illustrating a lane keeping assist system(LKAS) according to an embodiment of the present disclosure.

Referring to FIG. 1, the lane keeping assist system (LKAS) according tothe embodiment may include a plurality of sensing devices 10, anelectronic control unit (ECU) 20, and an electronic power steeringdevice. The sensing devices 10 may include a lane and preceding vehiclesensor 11, a vehicle dynamics sensor 12, etc. The ECU 20 may include alane and preceding vehicle recognition module, a route generation module22, and a target steering torque calculation module 23.

The lane and preceding vehicle sensor 11 may be implemented one or moreimage sensors, for example, a Far Infrared Ray (FIR) camera, a CMOScamera (or a CCD camera), etc. The lane and preceding vehicle sensor 11may be arranged at an upper end of a windshield of a host vehicle, maysense and project various kinds of light, for example, infrared light,visible light, etc., within the range of a predefined angle and apredefined distance with respect to a forward region of the hostvehicle, may acquire an image of an external object located adjacent tothe host vehicle, an image of a lane, etc., and may transmit therecognized images to the ECU 20.

The lane and preceding vehicle sensor 11 may be implemented as any ofvarious well-known sensors, such as a radar sensor, a Light DetectionAnd Ranging (LiDAR) sensor, etc. The lane and preceding vehicle sensor11 may include a plurality of sensors. The sensors may be respectivelyinstalled at a center part of a front surface, a center part of a rearsurface, and a corner part of the host vehicle, may emit electromagneticwaves within the range of a predetermined angle with respect to aforward region of each sensor, may receive electromagnetic wavesreflected from peripheral objects located in the vicinity of the hostvehicle, and may detect an angle, a distance, a relative speed, arelative acceleration, etc. between the host vehicle and each peripheralobject, such that the sensors of the lane and preceding vehicle sensor11 may transmit the detected information to the ECU 20.

The vehicle dynamics sensor 12 may be implemented as any of variouswell-known sensors, for example, a wheel speed sensor, an accelerationsensor, a yaw rate sensor, etc. The vehicle dynamics sensor 12 may bearranged at proper positions of a host vehicle, for example, a wheel, asteering wheel, or the like, such that the vehicle dynamics sensor 12may sense a driving speed, a steering angle, a yaw rate, etc. of thehost vehicle, and may transmit the sensed information to the ECU 20.

The ECU 20 of the vehicle may include a memory (e.g., DB) database suchas a Read Only Memory (ROM) or Random Access Memory (RAM), may storevarious control data such as a lane keeping assist (LKA) program, andmay further include a processor such as a CPU, such that the ECU 20 mayperform various control programs. The various modules of the ECU 20correspond to various functions performed by the processor byimplementing program instructions stored in the memory based on theinformation received by the ECU 20 from various sensors.

When the ECU 20 actively controls a traveling direction of the vehicleto follow a traveling route within a lane detected by the sensingdevices 10, if a lane capable of being temporarily recognized is notpresent or deterioration in lane recognition performance occurs, the ECU20 may perform the function of activating preceding vehicle followerlongitudinal control. Specifically, the ECU 20 may restrict a precedingvehicle follower longitudinal control range in a preceding vehiclefollower longitudinal control process caused by disappearance or loss ofa forward lane when lane keeping control is performed throughrecognition of a lane and a preceding vehicle, resulting in improvementin vehicle safety.

For this purpose, the lane and preceding vehicle recognition module 21may acquire lane and preceding vehicle sensing information from the laneand preceding vehicle sensor 11, and may recognize lane information andpreceding vehicle information. For example, the lane information mayinclude distance between the host vehicle and a left/right lane, adirection angle between the host vehicle and each lane, a curvature of aleft/right lane, a curvature change rate of a left/right lane, etc. Forexample, the preceding vehicle information may include ahorizontal/vertical distance between the host vehicle and the precedingvehicle, a difference in proceeding direction angle, etc. FIG. 2A is aconceptual diagram illustrating lane information recognized by the laneand preceding vehicle recognition module 21, and FIG. 2B is a conceptualdiagram illustrating preceding vehicle information recognized by thelane and preceding vehicle recognition module 21.

Subsequently, the route generation module 22 may generate a route suchthat the host vehicle can travel in the center of the lane based on lanerecognition information recognized by the lane and preceding vehiclerecognition module 21. During lateral control based on lane recognitionalong the generated route, when a lane capable of being temporarilyrecognized is not present or deterioration in lane recognitionperformance occurs (for example, when a vehicle enters a lanedisappearance section such as a crossroad, crosswalk, etc.), the routegeneration module 22 may generate a new route along which the hostvehicle follows the preceding vehicle based on preceding vehiclerecognition information recognized by the preceding vehicle recognitionmodule 21. Specifically, when the preceding vehicle deviates from thegenerated route during the preceding vehicle follower longitudinalcontrol (e.g., when the preceding vehicle performs lane change), theroute generation module 22 may restrict the preceding vehicle followerlongitudinal control range to avoid erroneous lane keeping control.

In other words, the route generation module 22 may determine whether thepreceding vehicle deviates from a current lane using final laneinformation during preceding vehicle follower longitudinal controlcaused by disappearance or loss of a forward lane, and may restrict thepreceding vehicle follower longitudinal control range based on thedetermined result. FIG. 3 is a conceptual diagram illustrating a methodfor deactivating preceding vehicle follower longitudinal control whenthe preceding vehicle deviates from the preceding vehicle followerlongitudinal control range after the route generation module 22determines whether lane departure of the preceding vehicle has occurredusing final lane information according to an embodiment of the presentdisclosure.

In more detail, the route generation module 22 may generate a virtuallane formed by extension of a conventional lane (as shown in FIG. 4) inconsideration of a curvature of the conventional lane based on finallane recognition information (e.g., a horizontal position of a hostvehicle within a lane, a direction angle between the host vehicle andthe lane, a curvature of the lane, and a curvature change rate of thelane) recognized by the lane and preceding vehicle recognition module 21within the lane disappearance section, and may generate a virtual routein a manner that the host vehicle can travel in the center of thevirtual lane. Thereafter, the ECU 20 may calculate the position of ahost vehicle in a virtual route and a direction angle of the hostvehicle by accumulating a driving speed, a steering angle, a yaw rate,etc. of the host vehicle detected by the vehicle dynamics sensor 12, andmay calculate a horizontal position about a virtual route of thepreceding vehicle by reflecting preceding vehicle recognitioninformation such as a horizontal/vertical distance between the hostvehicle and the preceding vehicle that are recognized by the lane andpreceding vehicle recognition module 21. The ECU 20 may determinewhether the preceding vehicle is traveling on the preceding vehiclefollower longitudinal control range of a virtual route through ahorizontal position about the calculated virtual route of the precedingvehicle. If the preceding vehicle travels in the preceding vehiclefollower longitudinal control range, the ECU 20 may continuously performthe preceding vehicle follower longitudinal control. During thepreceding vehicle follower longitudinal control process, if thepreceding vehicle deviates from the generated virtual route by apredetermined horizontal distance (i.e., if the preceding vehicledeviates from the preceding vehicle follower longitudinal controlrange), the ECU 20 may deactivate the preceding vehicle followerlongitudinal control. In this case, a reference value of the precedingvehicle follower longitudinal control range may be set to the width ofthe last lane centering around a virtual route generated by thepreceding vehicle follower longitudinal control range shown in FIG. 3.

The target steering torque calculation module 23 may calculate a targetsteering torque for following a target route generated by the routegeneration module 22, and may transmit the calculated target steeringtorque to the electronic power steering device 30.

The electronic power steering device 30 may generate a steering angle ofthe steering wheel upon receiving a control signal from the ECU 20, suchthat the electronic power steering device 30 may perform a lateralcontrol operation.

A lane keeping assist (LKA) method using the above-mentioned systemaccording to the present disclosure will hereinafter be described withreference to FIG. 5.

FIG. 5 is a flowchart illustrating an overall process of a lane keepingassist (LKA) method according to an embodiment of the presentdisclosure.

Referring to FIG. 5, if the lane keeping assist system (LKAS) is turnedon (S500), the ECU 200 may recognize a forward lane of the host vehicleusing the lane and preceding vehicle sensor 11 (YES in S510), and mayactively perform lane keeping control by adjusting a traveling directionof the vehicle such that the vehicle can follow the traveling routewithin the detected lane (S520).

If a lane capable of being recognized by the lane and preceding vehiclesensor 11 is not present or if deterioration in lane recognitionperformance occurs (NO in S510), the ECU 20 may store final lanerecognition information (e.g., a horizontal position of the host vehiclewithin the lane, a direction angle between the host vehicle and thelane, a curvature of the lane, and a curvature change rate of the lane)recognized by the lane and preceding vehicle recognition module 21, andmay store the stored information (S530). The ECU 20 may generate avirtual route formed by extension of a conventional lane inconsideration of a curvature of the conventional lane based on thestored final lane recognition information, such that the ECU 20 maygenerate a virtual route in a manner that the host vehicle can travel inthe center of the virtual lane (S540).

The ECU 20 may determine whether the preceding vehicle is present in aforward region of the host vehicle using the lane and preceding vehiclesensor 11 (S550). If the preceding vehicle is not present (NO in S550),the ECU 20 may deactivate lane keeping control of the lane keepingassist system (LKAS) (S560).

If the preceding vehicle of the host vehicle is detected (YES in S550),the ECU 20 may calculate a horizontal position of the preceding vehiclewithin the virtual route generated in step S540 (S570). The ECU 20 maydetermine whether the preceding vehicle is traveling within thepreceding vehicle follower longitudinal control range of the generatedvirtual route in consideration of a horizontal position about thecalculated horizontal position of the preceding vehicle (S580). If thepreceding vehicle travels within the preceding vehicle followerlongitudinal control range (YES in S580), the ECU 20 may performpreceding vehicle follower longitudinal control (S590). If the precedingvehicle deviates from the generated virtual route by a constanthorizontal distance (i.e., if the preceding vehicle deviates from thepreceding vehicle follower longitudinal control range) (No in S580), theECU 20 may deactivate lane keeping control of the lane keeping assistsystem (LKAS) (S560). In this case, a reference value of the precedingvehicle follower longitudinal control range may be set to the width ofthe last lane centering around the generated virtual route formed as thepreceding vehicle follower longitudinal control range shown in FIG. 3.

As is apparent from the above description, a lane keeping assist system(LKAS) and a method for controlling the same according to theembodiments of the present disclosure can restrict a preceding vehiclefollower longitudinal control range in a preceding vehicle followerlongitudinal control process caused by disappearance or loss of aforward lane when lane keeping control is performed through recognitionof a lane and a preceding vehicle, resulting in improvement in vehiclesafety.

Although a few embodiments of the present disclosure have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

What is claimed is:
 1. A lane keeping assist system for performing lanekeeping using information about a lane and peripheral vehiclecomprising: a lane and preceding vehicle sensor configured to detect aforward lane and a preceding vehicle with respect to a host vehicle; avehicle dynamics sensor configured to detect a driving speed, a steeringangle, and a yaw rate of the host vehicle; and an electronic controlunit (ECU) configured to control a traveling direction of the hostvehicle in a manner that the host vehicle follows a traveling routewithin the detected lane, perform a preceding vehicle following controlto control the traveling direction of the host vehicle to follow thepreceding vehicle if the lane is not detected, and restrict thepreceding vehicle follower control if the preceding vehicle deviatesfrom an expected path of travel.
 2. The lane keeping assist systemaccording to claim 1, wherein the electronic control unit (ECU)comprises a non-transitory memory and a processor, and is configured to:recognize lane information and preceding vehicle information byacquiring lane and preceding vehicle detection information from the laneand preceding vehicle sensor; generate a route for the host vehicle totravel in a center part based on the recognized lane information;generate a new route based on the recognized preceding vehicleinformation if the lane information is not recognized, and restrict thepreceding vehicle follower control if the preceding vehicle deviatesfrom the expected path of travel; and determine a target steering torqueneeded for the host vehicle following the generated route, and transmitthe determined target steering torque to an electronic power steeringdevice.
 3. The lane keeping assist system according to claim 2, whereinthe ECU is configured to restrict the preceding vehicle follower controlif the preceding vehicle deviates from the new route.
 4. The lanekeeping assist system according to claim 2, wherein: the laneinformation includes at least one of a horizontal position of the hostvehicle located in the lane, a direction angle between the host vehicleand the lane, a curvature of the lane, and a curvature change rate ofthe lane; and the preceding vehicle information includes at least one ofa horizontal/vertical distance between the host vehicle and thepreceding vehicle, and a difference in proceeding direction angle. 5.The lane keeping assist system according to claim 4, wherein: if thelane is not recognized, the ECU is configured to generate a virtual laneformed by extension of a legacy lane in consideration of a curvaturebased on finally-recognized lane information, and generate a virtualroute for the host vehicle to travel in a center part of the generatedvirtual lane.
 6. The lane keeping assist system according to claim 5,wherein: the ECU is configured to: determine a position and directionangle of the host vehicle present on the virtual route using the vehicledynamics sensor, determine a lateral position about the virtual route ofthe preceding vehicle by reflecting the preceding vehicle information inthe calculated information, and restrict the preceding vehicle followercontrol if the determined lateral position about the virtual route ofthe preceding vehicle deviates from the virtual route by a predeterminedlateral distance or greater.
 7. The lane keeping assist system accordingto claim 6, wherein a reference value of a lateral distance up to whichthe host vehicle follows the preceding vehicle based on the precedingvehicle follower control is set to a width of a final lane centeringaround the virtual route.
 8. A lane keeping assist method comprising: ifa lane keeping assist system configured to perform lane keeping usinginformation about a lane and peripheral vehicle is turned on, detectinga forward lane of a host vehicle; controlling a traveling route of thehost vehicle such that the host vehicle follows a traveling route withinthe detected lane if the lane is detected, or generating a virtual laneif the lane is not detected such that the host vehicle travels in acenter part of the virtual lane; detecting a preceding vehicle locatedin a forward region of the host vehicle; and deactivating the lanekeeping assist system if the preceding vehicle is not detected, orcontrolling a traveling direction of the host vehicle if the precedingvehicle is detected such that the host vehicle follows the precedingvehicle according to movement of the preceding vehicle.
 9. The lanekeeping assist method according to claim 8, wherein the virtual lane isformed by extension of a legacy lane based on finally-recognized laneinformation.
 10. The lane keeping assist method according to claim 8,wherein: the lane information includes at least one of a horizontalposition of the host vehicle located in the lane, a direction anglebetween the host vehicle and the lane, a curvature of the lane, and acurvature change rate of the lane; and the preceding vehicle informationincludes at least one of a horizontal/vertical distance between the hostvehicle and the preceding vehicle, and a difference in proceedingdirection angle.
 11. The lane keeping assist method according to claim10, wherein the controlling the traveling route of the host vehicle suchthat the host vehicle follows the preceding vehicle comprises:deactivating of the lane keeping assist system if the preceding vehicledeviates from the virtual route.
 12. The lane keeping assist methodaccording to claim 11, wherein the controlling the traveling directionof the host vehicle such that the host vehicle follows the precedingvehicle comprises: determining a horizontal position of the precedingvehicle within the virtual route; determining whether the precedingvehicle travels within a lateral distance, up to which the host vehiclefollows the preceding vehicle based on the preceding vehicle followercontrol, of the virtual route based on the determined horizontalposition of the preceding vehicle in the virtual route; and controllingthe traveling direction of the host vehicle if the preceding vehicletravels within the lateral distance such that the host vehicle followsthe preceding vehicle during traveling of the preceding vehicle, anddeactivating the lane keeping assist system if the preceding vehicledeviates from the virtual route by a predetermined horizontal distanceor greater.
 13. The lane keeping assist method according to claim 12,wherein a reference value of the lateral distance is set to a width of afinal lane centering around the virtual route.
 14. A lane keeping assistsystem comprising: an image sensor configured to detect a lane and apreceding vehicle ahead of a host vehicle; and an electronic controlunit comprising a non-volatile memory and a processor, and configuredto: receive information relating to the lane and the preceding vehiclefrom the image vehicle sensor, determine whether a lane or a precedingvehicle ahead of the host vehicle are recognized, perform, if a laneahead of the host vehicle is recognized, lane keeping control based onthe recognized lane, generate, if a lane ahead of the host vehicle isnot recognized, a virtual lane based on a final lane recognitioninformation and information relating to motion of the host vehicle,determine, if a preceding vehicle ahead of the host vehicle isrecognized, a position of the recognized preceding vehicle within thevirtual lane, perform, if a lateral distance, up to which the hostvehicle follows the preceding vehicle based on the preceding vehiclefollower control, of the recognized preceding vehicle is less than athreshold based on the virtual lane, preceding vehicle follower controlsuch that the host vehicle follows the preceding vehicle, and deactivatelane keeping control if no preceding vehicle is recognized ahead of thehost vehicle or if the lateral distance of recognized preceding vehicleis greater than the threshold.
 15. The lane keeping assist system ofclaim 14, wherein the ECU is configured to generate the virtual lane byextending a legacy lane based on the final lane recognition informationand a finally-recognized curvature of the legacy lane, and the ECU isfurther configured to generate a virtual route for the host vehicle totravel in a center part of the generated virtual lane.
 16. The lanekeeping assist system of claim 15, wherein the ECU is configured to:determine a position and direction angle of the host vehicle present onthe virtual route, determine a lateral position about the virtual routeof the preceding vehicle based on the information relating to thepreceding vehicle, and restrict the preceding vehicle follower controlif the determined lateral position about the virtual route of thepreceding vehicle deviates from the virtual route by more than thethreshold lateral distance.
 17. The lane keeping assist system of claim14, wherein the ECU is configured to perform the preceding vehiclefollower control by: generate, if a lane ahead of the host vehicle isnot recognized and a preceding vehicle is recognized, a new route basedon the recognized preceding vehicle information, determine a targetsteering torque needed for the host vehicle to follow the generatedroute, and transmit the determined target steering torque to anelectronic power steering device of the host vehicle.
 18. A lane keepingassist system comprising: an image sensor configured to detect a forwardlane and a preceding vehicle with respect to a host vehicle; and anelectronic control unit (ECU) configured to control a travelingdirection of the host vehicle by: performing lane keeping control, if alane ahead of the host vehicle is recognized, based on the recognizedlane, or if no lane ahead of the host vehicle is recognized, usingpreceding vehicle follower control based a recognized preceding vehiclethat is within a lateral distance up to which the host vehicle followsthe preceding vehicle based on the preceding vehicle follower control,and deactivating lane keeping control if no lane ahead of the hostvehicle is recognized and no preceding vehicle is recognized ahead ofthe host vehicle, or the lateral distance of the recognized precedingvehicle is greater than a threshold.
 19. The lane keeping assist systemof claim 18, wherein deactivating lane keeping control comprisesproviding control of the host vehicle to a driver of the host vehicle.20. The lane keeping assist system of claim 18, wherein the performinglane keeping control comprises: generating, if no lane ahead of the hostvehicle is recognized and a preceding vehicle is recognized, a new routebased on the recognized preceding vehicle, determining a target steeringtorque needed for the host vehicle to follow the generated route, andtransmitting the determined target steering torque to an electronicpower steering device of the host vehicle.
 21. The lane keeping assistsystem of claim 18, wherein the ECU is configured to: generate a virtuallane by extending a legacy lane based on a finally-recognized lane and afinally-recognized curvature of the legacy lane, and generate a virtualroute for the host vehicle to travel in a center part of the generatedvirtual lane.
 22. The lane keeping assist system of claim 21, wherein areference value of the lateral distance is set to a width of thefinally-recognized lane centering around the virtual route.